Tumor-associated antigens (TAA) on the surface of tumor cells growing in vivo may induce cellular and antibody-mediated immunological reactions in the tumor-bearing host. These reactions may inhibit or enhance tumor growth at local sites or be involved in facilitating or preventing spread, implantation and survival of tumor metastasis. The major objective of this proposal is to analyze the antibody responses of tumor-bearing mice to TAA on their own growing tumors by "capturing" and perpetuating part of the host's anti-TAA antibody repertoire in the form of hybridomas secreting monospecific anti-TAA antibodies. These monospecific antibodies will be used to identify and study TAA on a series of recently derived immunogenetically well characterized chemically induced murine tumors. Known TAA on these tumor lines include tumor specific transplantation antigens (TSTA), histocompatibility antigens H-2 and non-H2) and murine leukemia virus-associated antigens. The study includes the following additional objectives: 1. To compare the anti-TAA antibody responses of the tumor bearing host to syngeneic tumors classified as "immunogenic" or "non-immunogenic" based on TSTA strength. 2. To determine using specific monoclonal antibodies the antigenic relationship of tumor cells found in metastatic foci to those cells present in the original parent tumor. 3. To examine the antibody response of mice to their primary methylcholanthrene-induced tumors before the tumors are transplanted for the first time. 4. To assess in a preliminary way several monoclonal anti-TAA antibodies as mediators of anti-tumor immune reactions, particularly in antibody dependent cellular cytotoxicity reactions.